Control valve mechanism



May 14, 1940` w. F. BoLD'r CUNTROL VALVE MECHANISM Filed lay 18, 193e 2 Sheets-Sheet I LO mum-DOW 0.-.

INVENTOR F. BoLDT BY s ATTINEY.

May V14, 1940.

W. F. BOLDT CONTROL VALVE MECHANISM Filed May 18, 1938 2 Sheets-Sheet 2 o `8| 65 "sa 64 e2 o RowER FIG 4 CYLINDER 59 osouRcE oF PRESSURE mvENToR. w.l'.|ao| l ATTORNEY.

Patented May 14, 1940 PATENT OFFICE CONTROL VALVE MECHANISM Werner F. Boldt,

Clayton,

Mo., assigner to Wagner Electric Corporation, St. Louis, Mo., a

corporation of Delaware f Application May 18, 1938, Serial No. 208,560

16 Claims.

My invention relates to valve mechanism and more particularly to control valve mechanism for placing a source of iluid pressure or vacuum in communication With a movable member to be operated, as for example, the piston of a fluid motor.

One of the objects of my invention. is vto pro- I duce an improved control valve mechanism which will meter the fluid pressure or vacuum which is caused to be effective on the movable member which is to be operated.

Another object of my invention is to produce a control valve mechanism in which the valve element employed to connect the actuated member to the source of pressure'or suction and the valve element employed to connect the actuated member to the exhaust or atmosphere are unseated by a movement in the direction of flow of the uid and against a biasing means and to so control the biasing means that the pressure on one element can be increased and the pressure on the other element decreased in equal increments.

Still another object of my invention is to provide means in combination with the above valve mechanism which will produce a reactive effect noticeable by the operator in manipulations to vary the pressure or suction efiective on the member being operated.

Other objects of'my invention will become apparent from vthe following description taken in connection with the accompanying drawings in which Figure l is a cross-sectional view of a valve mechanism embodying myv invention and adapted for use in a uid pressure operated sys tem; Figure 2 is a cross-sectional view of a valve mechanism similar to that shown in Figure 1 but adapted for use in a vacuum-operated system; Figure 3 is a cross-sectional view of a valve mechanism similar to Figure 1 but embodying means for producing a reaction on the member controlled by the operator; and Figure 4 is a cross-sectional view taken on the line 4 4 of v Figure 3.

Referring to Figure 1,-numeral I indicates the casing of ther valve mechanism Within Whichis a chamber 2 adapted to be connected to the source of pressure by anvinlet port 3, a passage I anda conduit 5. 4The source of pressure for the valve mechanism shown is intended -to be compressed air but it is to be understood that other fluids under pressure may be employed. The .casing I is also provided with an exhaust port 6 in alignment with the inlet port 3 and this exhaust port is in communicationl with chamber 2 by means of a passage l. The chamber 2 in the casing is closed by a hollow end cap secured to the casing, and connected to the chamber by a passage in the cap is a conduit 9 placing the chamber in communication with the member to 5 be operated', as for example, a power cylinder for applying a braking assembly.

A reciprocable member I is supported by the casing and has one end projecting into chamber 2 upon which is mounted a lateral extending 10 arm I I. The other end of the reciprocable mem-A ber projects to the exterior of the casing and has mounted thereon a laterally extending arm I2. A seal comprising a packing I3, a spring I4 and .an expanding member I prevents leakage of 15 fluid past the reciprocable member.r

' The inlet port 3 is formed with a valve seat I6 and cooperating therewith is a valve element I'I which is so positioned as to be unseated` by movement in the direction of flow of uid under pressure through the inlet port from the source of pressure to chamber 2. The valve element is held in position on its seat by a coil spring I8 interposed between it and arm II carried by the inner end of the reciprocable member I0.

The exhaust port 6 is also provided with a valve seat I9 for cooperation with a Valve element 20 which is so positioned as to be movable off the seat in the direction of flow of fluid through the exhaust port from the chamber to the exterior of the casing. The valve elment 20 is held upon its seat by a coil spring 2| interposed betweenit and arm I2 carried by the exterior end of the reciprocable member.

The valve springs IB and 2| are preferably 35 identical in construction and characteristics and when the reciprocable member is in a position where arms II' and I2 are equal distances from the valve elements I'l and 20, respectively, the springs will maintain the valve elements on their o seats with the same pressure. The reciprocable member, however, is normally biased by a spring 22 to a position wherein spring 2l acting on the exhaust valve element 20 will be completely expanded and will exert no pressure or only a negligible pressure on the valve elment. The spring 22 is interposed between the shoulder 23 on the reciprocable member and a suitable portion 24 of the casing which acts as a bearing for the reciprocable member. The normal position of the reciprocable member is determined by the engagement of arm II with portion 25 of the casing.

The reciprocable member also carries a pin 26 cooperating with a slot 21 in the casing to thereby 55 prevent the reciprocable member from having relative rotation with respect to the casing. The exterior end of the reciprocable member and the exhaust port valve structure are enclosed by a suitable housing 28 secured to the main casing. The reciprocable member is operated by a suitable lever or pedal 29 connected to the recipro cable member by a rod 30 extending through an opening 3I in housing 28, which opening is of sucient size to permit the free passage from the housing of any air which may be exhausted through the exhaust port 6.

The strength of springs I8 and 2| for the valve elements is so chosen that the springs when compressed will maintain the valve elements seated against the maximum pressure which may be exerted thereon tending to unseat them. In other words, if the maximum iluid pressure is 100 pounds per square inch, for example, the spring I8 will be of sufficient strength to hold the valve element I1 seated and prevent fluid under pressure from passing from the source of pressure to chamber 2 when the reciprocable member is in the position shown in Figure 1. Spring 2|. since it is identical with spring I8, will also be of sulcient strength tomaintain the valve element 20 seated and prevent the fluid under maximum pressure from passing through the exhaust port when the reciprocable member is moved to its extreme right position.

When the valve mechanism is in the position shown in Figure 1, spring I8 will be compressed and valve element I1 will prevent uid under l pressure from entering the chamber from the source of pressure and since spring 2l is not exerting any pressure on valve element 20. there will not be any fluid under pressure in chamber 2 and the fluid motor which is to be operated. When it is desired to apply pressure to the member to be operated, the reciprocable member .I0 is moved t0 the right. I'his will cause spring 2| to begin to exert pressure on valve element 20 and spring I8 to apply less pressure to valve element I1. The increment of increase of pressure on valve element 20 is equal to the increment of decrease of pressure on valve element I1. When the pressure on the valve element is decreased suiiiciently to permit the fluid under pressure from the source of pressure to unseat valve element I1, fluidunder pressure will ow into chamber 2 until the pressure therein plus the spring pressure will be sufficient to close valve element I1. 'Ihe fluid pressure now in chamber 2 will notbe able to be exhausted from the chamber through exhaust port 6 because valve element 20 is held upon its seat by a pressure which is greater than the pressure which the fluid in chamber 2 is exerting on the valve element tending to unseat it.

Continued movement of the reciprocable mem ber to the right will cause the pressure on valve element I1 to be further decreased a given amount and the pressure on valve element 20 to be simultaneously increased a like amount. As the pressure on valve element I1 decreases, more fluid under pressure will be capable of entering chamber 2 and thus become effective on the member which is connected to conduit 9. When the reciprocable element has reached the end yof its travel vto the right, spring I8 will become totally expanded and the pressure on valve element I1 will be negligible. The pressure of the fluid in the chamber W'ill now be the same as that of the pressure source.

When it is desired to exhaust the fluid under ammassi pressure from chamber 2 and the fluid-operated member connected to conduit 9, the reciprocable member is allowed to move to the left under the action of spring 22. 'I'his will decrease the pressure on valve element 20 and simultaneously increase the pressure on valve element I1. As the pressure on valve element 20 decreases, the fluid under pressure on chamber 2 will be exhausted, the amount depending upon the pressure which is being exerted on the Valve element by spring 2l. When the reciprocable element has been returned to its normal inoperative position, as shown in Figure 1, spring 2I will exert no substantial pressure on the valve element and under these conditions, all of the uid under pressure in chamber 2 will be exhausted. During the movement of the reciprocable member to the left, no liuid will be able to pass valve element I1 since the uid under pressure in chamber 2 plus the pressure exerted by spring I 8 will maintain this valve seated.

During the operation of the valve mechanism the iluid under pressure in chamber 2 will exert some pressure on the end ofthe reciprocable member I0 tending to force it to the left. This pressure varies with the pressure of the fluid in the chamber and thus produces a variable reaction on the operator. In the construction shown the reaction is not great due to the small diameter of the reciprocable member but if a greater reaction is desired, it can be secured by increasing the diameter of the reciprocable member.

From the foregoing description it is apparent that I have constructed a control valve mechanism permitting iiuid under pressure to be applied to an operating member as desired. The pressure acting on the operating member can be increased or decreased in very small increments which is a very important feature since it permits the member to be applied and released very gradually.

Referring to Figure 2, I have disclosed my invention embodied in a valve mechanism for a vacuum-operated system. The casing member 32 is formed with a suction port 33 which is connected to the source of suction by the passage 34 and the conduit 35. 'I'he port 33 communicates with a chamber 36 in a second casing member 31 secured to the casing member 32. 'Ihe chamber 36 is in communication by a conduit 38 with a member to be operated, as for example, a vacuum motor. The casing member 32 is also provided with an atmospheric port 39 which is in communication with chamber 36 by a passage 40. 'Ihe atmospheric port is in alignment with the suction port 33.- The valve casing 32 has mounted thereon a reciprocable rod 4I which extends into chamber 36 and carries an arm 42. The other end of rod 4I projects to the exterior of casing 32 and carries an arm 43.

The suction port 33 has a valve seat 44 and cooperating therewith is a valve element having a fluted stem 46 slidable in the suction port. The valve element is positioned to be movable off seat 44 in the direction corresponding to the ow of fluid from chamber 36 to the source of suction which may be a manifold of an internal combustion engine. A coil spring 41 connects the valve element 45 to arm 42. The atmospheric port 39 has a valve seat 48 and cooperating therewith is a valve element 49 having a fluted stem 50 slidable inv the port. The valve element 49 is positioned to be movable off seat 46 in the direction of flow of fluid from the atmosphere to L "unseated by the action of suction.

chamber 36. A spring 5l connects the valve element 49 to arm 43. The reciprocable rod 4l is normally biased to the right-hand end of its travel by a spring 52 interposed between casing member 32 and arm 42, arm 43 under these conditions abutting the casing member 32. The reciprocable rod is actuated by rod 53 carried by casing member 31 and the outer end of this rod is engaged by an operating element 54 which may be a lever or a pedal. A perforated cap 54' encloses the exterior .end of rod 4l, arm 43 and spring 5l.

In the normal inoperative position of the valve mechanism, rod 4l will be in the right-hand end of its travel. Spring 5l will be `fully contracted and no substantial pressure will be exerted to hold valve element 49 seated. Spring 'lill under these conditions will be under tension and it will be exerting maximum effort to main- `tain the valve element 45 seated. The springs d1 and 5l are of identical construction and characteristics and they are of such strength that when expanded, the valve elements will not be To connect the source of suction to the suction motor, rod il is moved to the left and when in its extreme left position, as shown in Figure 2, the source of suction is capable of applying its maximum effect to operate the vacuum lmo- ,tor. Atmospheric pressure will be unable to pass through the atmospheric port 39 into chamber 36 because spring 5l is exerting its pressure upon 'the valve element Ml.

The general operation of the structure shown in Figure 2 is similar to that shown in Figure 1 yexcept that vacuum is employed instead of fluid *under pressure and to accommodate this change, the valve elements and the va-lve seats are reversed. The amount of air that is drawn from chamber 36 and the vacuum motor by the source of suction can be regulated to the desired extent by the forward movement of rod ll in the same manner as the pressure is regulated by the movement of the reciprocable member l@ in the previously described valve. Also, the amount of air sfrom the atmosphere that is admitted to chamiber 36 to release the suction motor can be regulated by the extent of return movement of rod M.

Referring to Figures 3 and 4, I have shown a :valve mechanism for use with a fiuid pressure 'system which is very similar to that disclosed in Figure 1 but has the additional feature of a lspring interposed between the actuating member and the longitudinally reciprocable member, which spring is adapted to be acted upon bv a piston carried by the reciprocable member and subject to the same fluid pressure which is effective on the member which is operated, as for example, the power cylinder. The` valve mechanism shown comprises a casing 55 provided with a fluid receiving chamber 56 having an inlet port 51 connected to a source of pressure by means of a passage 56 and a conduit 59. The chamber 56 is also connected to an exhaust port 66 by means of a passage 6I. The chamber is connected to the member to be operated. such as a power cylinder, by means of conduit 62 communicating with passage 6l. There is also provided a cover plate 63 for closing the end of the casing, the cover plate forming one wall of chamber 56. s

'I'he casing 5 5 is formed with a bore 64 within which is mounted the reciprocable member 65. The inner end of this member has mounted The inlet port has associated therewith a seat 69 and cooperating with the seat is a valve element 10 which is movable oli the seat in the direction of flow of uid from the source of pressure to chamber 56. A spring 1l is interposed lbetween arm 66 and the valve element. The exhaust port has associated therewith a suitable seat 12 and cooperating with this seat is a Valve element 13 which is movable off the seat 'in the direction of flow of fluid from the cham- 'ber 56 to the atmosphere. A coil spring 'lll is interposed between arm 61 on the reciprocable member and valve element 13. The springs 1l and 14 are of like construction and have the same characteristics and cooperate with their respective valve elements in the manner already set forth with respect to the construction shown in Figure 1.

The reciprocable member 65 is biased to its `normal inoperative position by a coil spring 15, thereby causing arm 66 to abut casing 55 as a stop and placing spring 1l under maximum compression. Under these conditions. coil spring' 1li 'will not be compressed and, therefore, apply only a negligible pressure to the valve element i3. The reciprocable element is actuated by an actuating member 16 which has bearing in a cap member l1 having an exhaust opening 18.. Interposed between the actuating member and the 'reciprocable member is a coil spring 19 which is in an uncompressed condition when the actuating member is not actuated and the reciprocable member is in its normal inoperative position as shown in Figure 3. The reciprocable member ls prevented from rotation relative to the casing by. a slot 66 and a pin di.

In. operation, movement of the reciprocable member 65 to the right will cause spring 1l to apply less pressure to the valve element 10 and the spring 1li to apply greater pressure to the valve element 13 whereby fluid under pressure 'will be admitted to chamber 56 and the power 'cylinder in a manner already described with relspect to the mechanism of Figure 1. Return i'novement of the reciprocable member to the left will cause spring 1l to be compressed and spring 14 to expand whereby the iiuid under 'pressure in chamber 56 andthe power cylinder 'will be exhausted to atmosphere. The amount of uid under pressure applied or released can be in small increments Since the movement of 'the reciprocable member causes the springs to increase and decrease the pressures on the valve elements in like increments. v

The use of spring 19 between actuating memvrber 16 and the reciprocable member 65 in com'- 'bination with the large end area of the reciprocable member which is subject tojthe pressure fof the fluid in chamber 56 results in a reaction on the actuating member 16. Since spring 19 has a rapid buildup, it will be compressed very little as the actuating member is initially operated to move the reciprocable member to the' right. As uid under pressure is'admitted to chamber `56, it will be elective on the end of the reciprocable member and willffcausethe reciprocable member to oat slightlyfto the left for i f -erator.

to be applied to the actuating member opposing 'the force applied to said member. This reaction force will be proportional to the pressure of the fluid in the chamber and, therefore, the

pressure acting on the power cylinder, thus giving the operator what is commonly known. as fee1. In other words, the greater the pressure rbeing applied, the greater will be the reaction on the actuating member and consequently the op- Spring 19, by permitting the recipro- -cable member to be initially moved beyond the 'position it iinally assumes after the fluid under 'pressure is admitted to chamber 56, results in la more rapid application of pressure since spring '1| will apply less pressure to valve element 10 v'during the admission of uid than it does after iiuid has been admitted.

Being aware of the possibility of other modifications in the particular structure herein described vvithout departing from the fundamental 'principles of my invention. I do not intend that its scope be limited except as set forth by the appended claims.

Having fully described my invention, what I i claim as new and desire to secure by Letters Patent of the United States is:

1. In a control valve mechanism, a casing provided with ports for supplying uid to and exhausting it from a chamber, a valve associated with cach port and movable oif its seat in the direction of iiow of uid through the port, means associated with each valve for applying pressure thereto to hold it in closed position, means for varying the pressure by which the means holds the supply port valve closed. and means subject to differential fluid pressures for causinga reactive effect on the last named means independently of the valves and the means for applying pressure thereto.

2. In a control valve mechanism, a casing provided With ports for supplying fluid to and exhausting it from a chamber, a Valve associated with each port and movable oft' its seat in the direction of ow of iiuid through the port, a biasing means associated with each valve for applying pressure thereto to hold it in closed position, means for varying the pressure exerted by each biasing means to hold the valves closed and means subject to the fluid pressure in said chamber for causing a reactive eiIect on said last named means independently of the valves and their=biasing means.

3. In a control valve mechanism, a. casing provided with ports for supplying iuid to and exl hausting it from a chamber, a valve associated with each port and movable off its seat in the direction o f flow of fluid through the port, a spring associated with each of said valves and applying pressure tending to hold it seated, means for increasing the pressure applied by one of said springs and simultaneously reducing the pressure applied by the other, said springs and said means being so related that the amount of increased pressure is substantially equal to the amount of reduced pressure. and a piston associated with said last named means and subject to the uid. pressure in the chamber for causing a reactive eiecton said last named means.

. 4. In a control valve mechanism, a casing provided with ports for supplying uid to and exhausting it from a chamber, a valve associated with each port and movable olf its'seatin the direction of flow of uid through the port, said ports being aligned and the opmng movanents of -the valves being in opposite directions, a

spring associated with each of the said valves, a member connected to each spring for control ling the pressure the spring applies to its valve, and means for moving the members in unison and in the same direction whereby an increasing pressure will be applied by one spring and a decreasing pressure will be applied by the other Spllng.

5. In a control valve mechanism, a casing provided with ports for supplying fluid to and exhausting it from a chamber, a valve associated with each port and movable off its seat in the direction of now of fluid through the port, said ports being aligned and the opening movements of the valves being in opposite directions, a spring associated with each of said valves, a member connected to each spring for controlling the pressure the spring applies to its valve, means for moving the members in unison and in the same direction whereby an increasing pressure will be applied by one spring and a decreasing pressure will be applied by the other spring, and a third spring associated with the last named means for biasing it to a position in which one of the valve springs will be applying a maximum pressure and the other a minimum pressure.

6. In a control valve mechanism, a. casing provided with ports for supplying fluid to and exhausting it from a chamber, a valve associated with each port and movable off its seat in the direction of ow of uid through the port, a compression spring associated with each valve and applying pressure tending to hold it seated, and a longitudinally movable member carrying an abutment for each spring, said abutments, valves and springs being so related that longitudinal movement of the movable member increases the compression of one spring and reduces the compression of the other.

'7. In a control valve mechanism for iiuid pressure, a casing provided with aligned inlet and exhaust ports and an outlet port, a valve element for the inlet port and positioned for movement off its seat in the direction of flow of uid from the inlet port to the outlet port, a coil spring for seating the valve element, a. second valve element for the exhaust port and positioned for movement olf its seat in the direction of flow of uid from the outlet port to the exhaust port, a coil spring for seating the second valve element, a reciprocable member, abutments on said reciprocable member for engaging the coil springs, said abutments being so spaced apart that when the reciprocable member is at one end of its travel the spring of the inlet valve element will be compressed and the spring of the exhaust valve element uncompressed and when the reciprocable member is at the other end of its travel the spring of the inlet valve element will be uncompressed and the spring of the exhaust valve element compressed. and means for reciprocating the reciprocable element.

8. In a control valve mechanism for iiuid pressure, a casing provided with aligned inlet and exhaust ports and an outlet port, a valve element for the inlet port and positioned for movement oi its seat in the direction of now of fluid from the inlet port to the outlet port, a coil spring for seating the valve element. a second valve elementfor the exhaust port and positioned for movement oil' its seat in the direction of ow of uid from the outlet port to the exhaust port, a coil spring for seating the second valve element, a reciprocable: memso spaced apart that when the reciprocable l member is at one end of its travellthe spring of the inlet valve element will be compressed and the spring of the exhaust valve element uncom-k pressed and when the reciprocable member is at the other end of its travel the spring of the inlet valve element will be uncompressed and the spring of the exhaust valve element compressed, a spring for normally biasing tha reciprocable element to one end of its travel, and means for l moving the reciprocable member against the last named biasing spring.

9. In a control valve mechanism, a casing provided with ports for supplying fluid to and exhausting it from a chamber, a valve associated with each port and movable oi its seat in the direction of ow of iiuid through the port, means for applying pressures to said valves tending tok hold them closed, said means being so associated with the valves that the pressure applied to one valve may be increased and the pressure applied to the other valve simultaneously reduced, an operator-operated member, and means associated with said means and subject to diierential iiuid pressures for causing a reactive eect on the operator-operated member.

l0. In a control valve mechanism, a casing provided with ports for supplying iiuid to and exhausting it from a chamber, a valve associated with each pom .and movable oi its seat in the direction of flow of luid through the port, a spring associated with each of said valves and applying pressure tending to hold it seated, means for increasing the pressure applied by one of said springs and simultaneously reducing the pressure applied by the other, an operatoroperated member, and means associated with said means and subject to differential uid pressures for causing .a reactive effect on the operator-operated member.

ll. In a control valve mechanism, a casing provided with aligned ports for supplying iluid to and exhausting it from a chamber, valve elements associated with the ports and each movable oi its seat in the direction of flow of iuid through the port, springs for holding the valve elements seated, a reciprocable member, means carried by the reciprocable member for causing one of the springs to apply an increasing pressure to its valve element and simultaneously permitting the other spring to apply a decreasing pressure to its valve element, spring means cooperating with the reciprocable member for normally causing it to assume a position wherein the valve element forone of the ports is maintained seated under maximum pressure and the valve element for .the other port is maintained seated under minimum pressure, and means associated with the reciprocable member and subject to the diierential pressure between the pressure of the uid in the casing and the atmospheric pressure for r,causing a reaction to movement of the reciprocable member.

12. In a control valve mechanism, a casing provided with ports for supplying fluid to and exhausting it from a chamber, valve elements associated with the ports` and each movable olf its seat in the direction of ow of duid through the port, means for simultaneously causing an increasing closing pressure to be exerted on one of the valves and a decreasing closing pressure to be exerted on the other valve, operator-operated means for actuating said means, and means associated with the rst named means and subject to the diierential pressure between the iluid pressure in the casing and the atmospheric pressure for causing a reaction on the` operator-operated means.

i3. In a control valve mechanism for fluid npressure, a casing provided with aligned inlet and exhaust ports and an outlet port, a valve element for the inlet port and positioned for movement od its seat in the directionoi flow of fluid from the inlet port to the outlet port, a coil springior seating the valve element, a second valve element for the exhaust port and positioned for movement ofi its seat in the direction of ow of fluid from the outlet port to the exhaust port, a coil spring for seating the second valve element, a reciprocable member, abutments on said reciprocable member for engaging the coil springs, Said abutments being so spaced apart that when the reciprocable member is at' one end of its travel the spring of the inlet valve element will be compressed and the spring of the exhaust valve element uncompressed and when the reciprocable member is at the other end of its travel the spring of the inlet valve element will be uncompressed and the spring of the exhaust valve elementcompressed, a spring for normally biasing the reciprocable element to one end oi its travel, means for moving the recipro-Q cable member against the last named biasing spring, and a piston carried by the reciprocable element and vbeing subject to the pressure'of the iiuid in the casing.

14. In a control valve mechanism for fluid pressure, a casing provided with aligned inlet and exhaust ports and an outlet port, a valve element for the inlet port and positioned for movement o" its seat in the direction of iiow of uid fromthe inlet port to the outlet pom, a coil spring for seating the valve element, a second valve element for the exhaust port and positioned for movement off its seat in the direction of :How of fluid from the outlet port to the exhaust port, a coil spring for seating the second valve element, a reciprocable member, abutments on said reciprocable member for engaging the coil springs, said abutments being so spaced apart that when the reciprocable member. is at one end of its travel the spring of the inletvalve element be compressed and the spring of the exhaust valve element uncompressed and when the reciprocable member is at the other end of its travel the spring of the inlet valve element will be uncompressed and the spring of the exhaust valve element compressed, a spring for normally biasing the reciprocable element to one end of its travel, means for moving the re ciprocable member against the last named biasing spring, a spring interposed Ibetween said last named means and the reciprocable member, and a piston carried by the reciprocable element and being subject to the pressure of the fluid in the casing. j

15. In a control valve mechanism, a casing provided with a chamber having a port for connection with a source of suction, a second port for connection with the atmosphere and a third port for connection with a suction-operated member, a valve 'element associated with the first named port and l'positioned for movement off its seat in the direction of flow of uid from the chamber to the source of suction, a valve element associated with the second port and positioned for movement off its seatin the direction of ow of fluid from the atmosphere to the chamber, the opening movements of said valve elements being in opposite directions, a reciprocable member, and tension means between each of the valve elements and the reciprocabie member, said tension means being so associated with the reciprocable member and the valve elements and having such characteristics that one of the valve elements will be held seated with a maximum pressure and the other valve element will be seated with substantially no pressure when the recprocable member is at one end of its travel and when the reciprocable member is at the other end of its travel the pressure on the valve elements will be reversed.

16. In a control valve mechanism, a casing provided with a chamber having a port for connection with a source of suction, a second port aligned with the rst named port for connection with the atmosphere and a third port for connection with a suction-operated motor, a valve element associated with the rst named port and positioned for movement ofiv its seat in the direction of flow of uid from the chamber to the source of suction, a valve element associated with the second port and positioned for movement off its seat in the direction of flow of fluid from the atmosphere to the chamber, the opening movements of said valve elements being in opposite directions, a reciprocable member, arms carried by the member and positioned on opposite sides of the aligned ports, tension springs of like characteristics for connecting the valves to the arms of the reciprocable member, means for normally biasing the reciprocable member to a position where the spring connected to the valve element of the first port will exert a maximum pressure thereon to hold it'seated and the spring connected to the valve element of the second port will exert substantially no pressure thereon tending to hold it seated, and means for moving the reciprocable member against its biasing means. WERNER F. BOLDT. 

